Assembly
Download as PPT, PDF1 like903 views
The document discusses 7 basic CPU instructions - MOV, XCHG, ADD, SUB, INC, DEC, NEG - for transferring data and doing arithmetic. It provides the syntax and examples of using each instruction to move data between registers and memory locations, exchange register contents, add and subtract values, increment and decrement, and negate values. It also shows examples of translating statements into assembly language code using these instructions to calculate a series summation.
Assembly
- 1. 1
- 2. 2 A FEW BASICA FEW BASIC INSTRUCTIONSINSTRUCTIONS
- 3. Presented By
- 4. Contents
- 5. There are over a hundred instructions in the instruction set for the 8086 CPU. Here we discuss 7 of the most useful instructions for transferring data and doing arithmetic. The discussed instructions are…….. MOV,XCHG,ADD,SUB,INC,DEC,NEG. 5 IntroductionIntroduction
- 6. MOVMOV Transfer data ◦ Between registers ◦ Between register and a memory location ◦ Move a no. directly to a register or a memory location Syntax MOV destination, source Example MOV AX, WORD1 6 How?
- 7. XCHG Exchange the contents of ◦ Two registers ◦ Register and a memory location Syntax XCHG destination, source Example XCHG AH, BL 7 AL BL 00 1A 05 00 AH AL BH BL How?
- 8. Legal Combinations of Operands forLegal Combinations of Operands for MOV And XCHGMOV And XCHG Destina tion Operan d Source Opera nd Legal General Register General Register YES General Register Memory Locatio n YES Memory Location General Register YES Memory Location Memory Locatio n NO Destination Operand Source Operand Legal General Register General Register YES General Register Memory Location YES General Register Segment Register YES General Register Constant YES Memory Location General Register YES Memory Location Memory Location NO Memory Location Segment Register YES Memory Constant YES MOV XCHG
- 9. ADD InstructionADD Instruction To add contents of: ◦ Two registers ◦ A register and a memory location ◦ A number to a register ◦ A number to a memory location Example ADD WORD1, AX 9 How?
- 10. SUB InstructionSUB Instruction To subtract the contents of: ◦ Two registers ◦ A register and a memory location ◦ A number from a register ◦ A number from a memory location Example SUB AX, DX 10 How?
- 11. Legal Combinations of Operands forLegal Combinations of Operands for ADD & SUB instructionsADD & SUB instructions 11 Destination Operand Source Operand Legal General Register General Register YES General Register Memory Location YES General Register Constant YES Memory Location General Register YES Memory Location Memory Location NO Memory Location Constant YES
- 12. INC & DECINC & DEC INC (increment) instruction is used to add 1 to the contents of a register or memory location. ◦ Syntax: INC destination ◦ Example: INC WORD1 DEC (decrement) instruction is used to subtract 1 from the contents of a register or memory location. ◦ Syntax: DEC destination ◦ Example: DEC BYTE1 12 Destination can be 8-bit or 16-bits wide. Destination can be a register or a memory location.
- 13. 13 INC WORD1 DEC BYTE1 INC & DECINC & DEC How? How?
- 14. NEGNEG Used to negate the contents of destination. Replace the contents by its 2’s complement. Syntax: NEG destination Example: NEG BX 14How?
- 15. ExamplesExamples Consider instructions: MOV, ADD, SUB, INC, DEC, NEG A and B are two word variables Translate statements into assembly language: 15 Statement Translation A =-( A+1) MOV AX,A INC AX NEG AX MOV A,AX B= 3B-7 MOV AX,B ADD AX,B ADD AX,B SUB AX,7 MOV B,AX Example:1 Example:2 Statem ent Translation A = B – A-1 MOV AX,B SUB AX,A DEC AX MOV A,AX Example:3
- 16. 16 ApplicationApplication .data msg1 DB 'Input Any number From 1 To 9:$' ; Data segment msg2 DB 'The Series Summation Is:$' .code main proc mov AX,@DATA ; Data segment mov DS,AX lea dx,msg1 ;showing msg1 mov ah,9 int 21h mov ah,1 ;taking input int 21h xor ah,ah sub al,30h XOR CX,CX ;loop same as input mov cx,ax XOR bx,bx ## A series summation of n numbers where 1<=n<=9
- 17. 17 sub bx,0Ah add ax,1 ;counter=ax=3 CMP bx ,39h ;bx<39h JL DISPLAY sub bx,0Ah add ax,1 ;counter=ax=4 CMP bx ,39h ;bx<39h JL DISPLAY DISPLAY: add al,30h mov cl,al lea dx,msg2 ;showing msg2 mov ah,9 int 21h mov ah,2 mov dl,cl int 21h mov dl,bl int 21h ApplicationApplication TOP: add bx,cx ;adding LOOP TOP mov ah,2 mov dl,0Dh int 21h ;printing new line mov dl,0Ah int 21h xor ax,ax add bx,30h CMP bx ,39h ;bx<39h JL DISPLAY sub bx,0Ah add ax,1 ;counter=ax=1 CMP bx ,39h ;bx<39h JL DISPLAY sub bx,0Ah add ax,1 ;counter=ax=2 CMP bx ,39h ;bx<39h JL DISPLAY
- 18. 18
- 19. ? ? <